This invention relates to apparatus for coupling a small video camera to an optical endoscopic probe to enable the optical image produced by the probe to be converted to a video picture.
Sims in U.S. Pat. No. 4,655,569 discloses an eyepiece adaptor for coupling an optical endoscope to the lens barrel of a self-contained camera. The adaptor is threaded into the lens barrel of the camera and the proximal end of the endoscope is inserted into the front of the adaptor. A split-collar is passed over the probe and threaded into the front of the adaptor to lock the probe in alignment with the camera lens. Once the probe is locked in place, moisture can be trapped in the region separating the endoscope and the camera lens barrel. Any moisture in this area will coat the exposed optical elements and thus seriously degrade the target image. When this occurs, the adaptor must be dismantled and the optical element cleaned.
Makepeace et al, in U.S. Pat. No. 3,900,021 also describes a similar adaptor for coupling an endoscope to a self-contained camera. The adaptor has a magnetic coupling that permits the endoscope to be rotated about the camera lens axis. Here again, no provision is made for removing moisture that might have developed inside the adaptor housing and the exposed optical elements will become contaminated as moisture builds up in this region.
Underhill Jr., in an earlier U.S. Pat. No. 2,465,764 describes a cylindrical lens barrel for use in a motion picture camera. The lens barrel is arranged to conduct light from a high intensity lamp to a film strip so as to project an image of the data recorded on the film strip to a viewing screen. As noted by Underhill Jr., oil used in this type of motion picture camera oftentimes finds its way into the lens system and coats the optical elements. Underhill Jr. passes a small relief tube into his lens barrel which allows air to pass into and out of the barrel. When the optical elements within the barrel are heated by the lamp, ambient air is drawn into the barrel through the tube. The air is later expelled when the lamp is turned off and the barrel cools. This constant exchange of air permits the barrel to "breathe" and thus expel unwanted oil collected in the lens barrel. The tube is packed with absorbent material which collects the expelled oil. Most modern-day cameras, and in particular, solid state cameras, are not subjected to oil contamination nor are they subjected to extreme changes in temperatures. The breathing technique described by Underhill Jr. therefore is of little or no use in these types of cameras.
Camera adaptors have been developed for use in endoscopes which are capable of coupling an optical probe to a video system so that an enlarged picture of the target can be presented upon a television screen. The proximal end of the probe is generally relatively small and, as a consequence, the adaptors are correspondingly small. Little room is thus afforded within the adaptor for mounting apparatus for preventing or removing moisture. Attempts directed toward locating this type of equipment within this limited space, have proven to be generally unsatisfactory.